Front bias magnetic speed sensor with true-power-on capability

ABSTRACT

A magnetic sensor system includes a toothed wheel configured to rotate about a rotation axis that extends in an axial direction, wherein the toothed wheel includes a plurality of teeth and a plurality of notches arranged that define a circumferential perimeter, wherein the toothed wheel further includes an interior cavity arranged within the circumferential perimeter; a front-bias magnet arranged within the interior cavity of the toothed wheel, wherein the front-bias magnet is rotationally fixed and is magnetized with a magnetization direction that extends along a radial axis of the toothed wheel; and a magnetic sensor arranged exterior to the toothed wheel, wherein the magnetic sensor includes a sensor element arranged on the radial axis that coincides with the magnetization direction of the front-bias magnet and the first sensor element is sensitive to a magnetic field of the front-bias magnet that is aligned with the radial axis.

FIELD

The present disclosure relates generally to sensing a rotational speedof a target object, and, more particularly, to magnetic speed sensors.

BACKGROUND

To measure a rotational speed of a toothed wheel, for example, typicallya ferromagnetic toothed wheel is used in combination with a magneticsensitive sensor and a back-bias magnet mounted to the sensor. Thesensor generates output-pulses. A control unit counts the pulses and isable to calculate the rotational speed and actual angle of the rotatingwheel, as well as optionally determine the rotation direction of thewheel.

In camshaft sensing applications, a Hall monocell configuration may beused that enables output switching at the tooth edge of a toothed wheel.A z-magnetized back-bias sensor in combination with the Bz-sensitivemonocell sensor generates a sinusoidal signal as the ferrous targetwheel rotates in front of the sensor. A back-bias magnet produces astatic magnetic bias field at the sensing elements, which is deflectedand modulated when the tooth wheel rotates. The maximum amplitude isachieved when a tooth center passes the sensor, while the minimum signalis achieved when the sensor faces a notch center of the toothed wheel.Thus, the sensor device switches on the tooth edge.

A benefit in using a Hall monocell sensor is that the sensor istwist-insensitive such that the sensor will work independent from amounting position regardless of its rotational orientation around itsz-axis. Thus, an air-gap between the sensor module and the wheel can beadjusted during mounting using a screw. That is, twisting the sensormodule like a screw will adjust the air-gap and the rotationalorientation of the sensor can be disregarded. Accordingly, the assemblytolerances are relaxed during mounting of the sensor due to thetwist-insensitivity.

On the downside, Hall monocell sensors have a disadvantage in terms ofstray-field robustness. Stray-fields are magnetic fields that areintroduced by external means located in the proximal environment of thesensor. For example, components located within a vehicle (e.g., forhybrid cars due to current rails driving high electrical currents closeto the sensing device or due to inductive battery charging) or acurrents flowing through a railway of a train system that generatesmagnetic fields may cause stray-field disturbance. External magneticstray-fields directly affect the magnetic signal and in worst case couldlead to wrong position information.

In camshaft sensing applications, an engine control unit (ECU) can usethe magnetic speed sensors to detect the exact position of the camshaft.This precise information helps to control the fuel injection and theintake and exhaust valves, thereby increasing the overall performanceand efficiency of a vehicle and ultimately reduces the emissions.True-power-on (TPO) is a feature that enables a fast start up. Directlyat start-up, the magnetic speed sensor can provide the precise positionof the camshaft (e.g., information indicating whether the sensor isfacing a tooth or a notch of the cam target wheel). Providing thisinformation to the ECU with high accuracy enables advanced controlschemes like variable camshaft adjustment (variable valve timing (VVT))which improves the performance, fuel economy, or emissions of a vehicleby a precise timing of the injection and ignition phase.

Typical camshaft sensors use a “zero-gauss” magnet for the back-biasmagnet, which is typically a magnet that has a center axis with a centerbore or a center cavity that extends axially along the center axis. Themagnet needs to be axially magnetized and a sensing element (e.g., aHall monocell) is concentrically aligned with the magnet's center axis.As a result of the center bore, the magnet produces essentially a 0 mTmagnetic field in the sensor plane at the position of one or moresensing elements. This zero magnetic field in the sensor plane isreferred to as a zero magnetic offset and is intended to be present inthe absence of a ferromagnetic target. In the case of a toothed wheel,the zero magnetic offset occurs in the sensor plane in the absence of atooth or, alternatively, in the presence of a notch.

This special magnet is required for the TPO feature. At a notch centerof the toothed wheel, the back-bias magnet produces essentially a 0 mTmagnetic offset at the Hall plate location. If a tooth passes thesensor, the magnetic offset increases. Therefore, the magnetic signal isan imprint of the mechanical wheel shape (e.g., an imprint of thetooth-notch pattern directly visible in the magnetic signal). The lowmagnetic offset in the notch center is crucial for a reliable TPOfunctionality over lifetime. A small magnetic offset (ideally 0 mT) isless affected by temperature drifts and aging effects (e.g., loss ofmagnetic strength over lifetime). Also independent from mountingtolerances (air-gap variances), the magnetic offset in the notch will beconstantly small.

Therefore, with a good magnet design that provides low magnetic offset,one can program a TPO threshold value which is used for the decisionwhether the sensor is currently facing a tooth or a notch. Thanks to thelow magnetic offset aging, temperature effects of the magnet, andmounting tolerances (air-gap variances) of the device will not affectthe accuracy of the sensor.

One disadvantage of such a setup is that zero-gauss magnets areexpensive. The magnet shape needed to produce a 0 mT magnetic offset inthe sensor plane in all sensing directions is rather complex and cannotbe produced in high volume by simple mechanical machining processes likeslicing, grinding, or drilling. Instead, the magnets need to bemanufactured using an expensive mold injection process or a one-by-onesingle-part sinter tooling process. Due to brittleness of sinteredmagnets, it is rather challenging to produce the magnets by mechanicalprocess (slicing, drilling, grinding). More expensive, higher-gradematerials and more expensive processes are required.

Therefore, an improved magnetic sensing system that is stray-fieldrobust, twist-insensitive (i.e., twist independent), and is lessexpensive to manufacture may be desirable.

SUMMARY

Magnetic sensor modules, systems and methods are provided, configured todetect a rotation of an object, and, and more particularly, to detect aspeed of rotation of an object.

One of more embodiments provide a magnetic sensor system, including: atoothed wheel configured to rotate about a rotation axis that extends inan axial direction, wherein the toothed wheel includes a plurality ofteeth and a plurality of notches arranged in an alternating tooth-notchpattern and which define a circumferential perimeter, wherein thetoothed wheel further includes an interior cavity arranged within thecircumferential perimeter; a front-bias magnet arranged within theinterior cavity of the toothed wheel, wherein the front-bias magnet isrotationally fixed and is magnetized with a magnetization direction thatextends along a radial axis of the toothed wheel, the radial axis beingorthogonal to the rotation axis; and a magnetic sensor arranged exteriorto the toothed wheel, wherein the magnetic sensor includes a firstsensor element arranged on the radial axis that coincides with themagnetization direction of the front-bias magnet and the first sensorelement is sensitive to a magnetic field of the front-bias magnet thatis aligned with the radial axis, wherein a rotation of the toothed wheelcauses the magnetic field to oscillate between a first extremum valueand a second extremum value at a location of the first sensor element.

One of more embodiments provide a magnetic sensor system, including: atoothed wheel configured to rotate about a rotation axis that extends inan axial direction, wherein the toothed wheel includes a plurality ofteeth and a plurality of notches arranged in an alternating tooth-notchpattern and which define a circumferential perimeter, wherein thetoothed wheel further includes an interior cavity arranged within thecircumferential perimeter; a front-bias magnet arranged exterior to thetoothed wheel, wherein the front-bias magnet is rotationally fixed andis magnetized with a magnetization direction that extends along a radialaxis of the toothed wheel, the radial axis being orthogonal to therotation axis; and a magnetic sensor arranged within the interior cavityof the toothed wheel, wherein the magnetic sensor includes a firstsensor element arranged on the radial axis that coincides with themagnetization direction of the front-bias magnet and the first sensorelement is sensitive to a magnetic field of the front-bias magnet thatis aligned with the radial axis, wherein a rotation of the toothed wheelcauses the magnetic field to oscillate between a first extremum valueand a second extremum value at a location of the first sensor element.

One of more embodiments provide a magnetic sensor module, including: afront-bias magnet magnetized with a magnetization direction that extendsalong a symmetry axis of the front-bias magnet; a magnetic sensorincluding a first sensor element arranged on an extension of thesymmetry axis that coincides with the magnetization direction of thefront-bias magnet, wherein the first sensor element is sensitive to amagnetic field of the front-bias magnet that is aligned with the radialaxis; and a molded package that encapsulates the front-bias magnet andthe magnetic sensor, wherein the molded package includes a package notchformed between the front-bias magnet and the magnetic sensor along theextension of the symmetry axis, wherein the package notch is formed toenable a plurality of teeth of a toothed wheel to pass through thepackage notch during a rotation of the toothed wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described herein making reference to the appendeddrawings.

FIGS. 1A and 1B illustrate a magnetic field sensing principle of amagnetic sensor system according to one or more embodiments;

FIG. 2 illustrates a cross-sectional view of a magnetic sensor systemaccording to one or more embodiments;

FIG. 3 illustrates a cross-sectional view of a magnetic sensor systemaccording to one or more embodiments;

FIG. 4 illustrates a cross-sectional view of a magnetic sensor systemaccording to one or more embodiments;

FIG. 5A is a schematic block diagram of a sensor circuit for a monocellsensing configuration according to one or more embodiments;

FIG. 5B is a schematic block diagram of a sensor circuit for adifferential sensing configuration according to one or more embodiments;and

FIGS. 6A and 6B illustrate sensor packages according to one or moreembodiments.

DETAILED DESCRIPTION

In the following, details are set forth to provide a more thoroughexplanation of the exemplary embodiments. However, it will be apparentto those skilled in the art that embodiments may be practiced withoutthese specific details. In other instances, well-known structures anddevices are shown in block diagram form or in a schematic view ratherthan in detail in order to avoid obscuring the embodiments. In addition,features of the different embodiments described hereinafter may becombined with each other, unless specifically noted otherwise. It isalso to be understood that other embodiments may be utilized andstructural or logical changes may be made without departing from thescope defined by the claims. The following detailed description,therefore, is not to be taken in a limiting sense.

Further, equivalent or like elements or elements with equivalent or likefunctionality are denoted in the following description with equivalentor like reference numerals. As the same or functionally equivalentelements are given the same reference numbers in the figures, a repeateddescription for elements provided with the same reference numbers may beomitted. Hence, descriptions provided for elements having the same orlike reference numbers are mutually exchangeable.

Directional terminology, such as “top”, “bottom”, “above”, “below”,“front”, “back”, “behind”, “leading”, “trailing”, “over”, “under”, etc.,may be used with reference to the orientation of the figures and/orelements being described. Because the embodiments can be positioned in anumber of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. In someinstances, directional terminology may be exchanged with equivalentdirectional terminology based on the orientation of an embodiment solong as the general directional relationships between elements, and thegeneral purpose thereof, is maintained.

In the present disclosure, expressions including ordinal numbers, suchas “first”, “second”, and/or the like, may modify various elements.However, such elements are not limited by the above expressions. Forexample, the above expressions do not limit the sequence and/orimportance of the elements. The above expressions are used merely forthe purpose of distinguishing an element from the other elements. Forexample, a first box and a second box indicate different boxes, althoughboth are boxes. For further example, a first element could be termed asecond element, and similarly, a second element could also be termed afirst element without departing from the scope of the presentdisclosure.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

In embodiments described herein or shown in the drawings, any directelectrical connection or coupling, i.e., any connection or couplingwithout additional intervening elements, may also be implemented by anindirect connection or coupling, i.e., a connection or coupling with oneor more additional intervening elements, or vice versa, as long as thegeneral purpose of the connection or coupling, for example, to transmita certain kind of signal or to transmit a certain kind of information,is essentially maintained. Features from different embodiments may becombined to form further embodiments. For example, variations ormodifications described with respect to one of the embodiments may alsobe applicable to other embodiments unless noted to the contrary.

Depending on certain implementation requirements, a storage medium mayinclude a RAM, a ROM, a PROM, an EPROM, an EEPROM, a FLASH memory, orany other medium having electronically readable control signals storedthereon, which cooperate (or are capable of cooperating) with aprogrammable computer system such that the respective method isperformed. Therefore, a storage medium may be regarded as anon-transitory storage medium that is computer readable.

Additionally, instructions may be executed by one or more processors,such as one or more central processing units (CPU), digital signalprocessors (DSPs), general purpose microprocessors, application specificintegrated circuits (ASICs), field programmable logic arrays (FPGAs), orother equivalent integrated or discrete logic circuitry. Accordingly,the term “processor,” as used herein refers to any of the foregoingstructure or any other structure suitable for implementation of thetechniques described herein. In addition, in some aspects, thefunctionality described herein may be provided within dedicated hardwareand/or software modules. Also, the techniques could be fully implementedin one or more circuits or logic elements. A “controller,” including oneor more processors, may use electrical signals and digital algorithms toperform its receptive, analytic, and control functions, which mayfurther include corrective functions.

Signal conditioning, as used herein, refers to manipulating an analogsignal in such a way that the signal meets the requirements of a nextstage for further processing. Signal conditioning may include convertingfrom analog to digital (e.g., via an analog-to-digital converter),amplification, filtering, converting, biasing, range matching, isolationand any other processes required to make a sensor output suitable forprocessing after conditioning.

Embodiments relate to sensors and sensor systems, and to obtaininginformation about sensors and sensor systems. A sensor may refer to acomponent which converts a physical quantity to be measured to anelectric signal, for example, a current signal or a voltage signal. Thephysical quantity may for example comprise a magnetic field, an electricfield, a pressure, a force, a current or a voltage, but is not limitedthereto. A sensor device, as described herein, may be a speed sensorthat measures a rotational speed of an object, such as a toothed wheel.

A magnetic field sensor, for example, includes one or more magneticfield sensor elements that measure one or more characteristics of amagnetic field (e.g., an amount of magnetic field flux density, a fieldstrength, a field angle, a field direction, a field orientation, etc.).The magnetic field may be produced by a magnet, a current-carryingconductor (e.g., a wire), the Earth, or other magnetic field source.Each magnetic field sensor element is configured to generate a sensorsignal (e.g., a voltage signal) in response to one or more magneticfields impinging on the sensor element. Thus, a sensor signal isindicative of the magnitude and/or the orientation of the magnetic fieldimpinging on the sensor element.

According to one or more embodiments, a magnetic field sensor and asensor circuit are both accommodated (i.e., integrated) in the same chippackage (e.g., a plastic encapsulated package, such as leaded package orleadless package, or a surface mounted device (SMD)-package). This chippackage is also referred to as sensor package. The sensor package may becombined with a back-bias magnet to form a sensor module, sensor device,or the like.

One or more magnetic field sensor elements, or for short a magneticfield sensors, included in the sensor package is thus exposed to themagnetic field, and the sensor signal (e.g., a voltage signal) providedby each magnetic field sensor element is proportional to the magnitudeof the magnetic field, for example. Further, it will be appreciated thatthe terms “sensor” and “sensing element” may be used interchangeablythroughout this description, and the terms “sensor signal” and“measurement value” may be used interchangeably throughout thisdescription.

The sensor circuit may be referred to as a signal processing circuitand/or a signal conditioning circuit that receives the signal (i.e.,sensor signal) from the magnetic field sensor element in the form of rawmeasurement data and derives, from the sensor signal, a measurementsignal that represents the magnetic field. The sensor circuit mayinclude a digital converter (ADC) that converts the analog signal fromthe one or more sensor elements to a digital signal. The sensor circuitmay also include a digital signal processor (DSP) that performs someprocessing on the digital signal, to be discussed below. Therefore, thesensor package comprises a circuit which conditions and amplifies thesmall signal of the magnetic field sensor via signal processing and/orconditioning.

A sensor device, as used herein, may refer to a device which includes asensor and sensor circuit as described above. A sensor device may beintegrated on a single semiconductor die (e.g., silicon die or chip),although, in other embodiments, a plurality of dies may be used forimplementing a sensor device. Thus, the sensor and the sensor circuitare disposed on either the same semiconductor die or on multiple dies inthe same package. For example, the sensor might be on one die and thesensor circuit on another die such that they are electrically connectedto each other within the package. In this case, the dies may becomprised of the same or different semiconductor materials, such as GaAsand Si, or the sensor might be sputtered to a ceramic or glass platelet,which is not a semiconductor.

Magnetic field sensor elements include, but is not limited to, lateralHall effect devices, vertical Hall effect devices, or magneto-resistivesensors, often referred to as XMR sensors which is a collective term foranisotropic magneto-resistive (AMR), giant magneto-resistive (GMR),tunneling magneto-resistive (TMR), etc.

Magnetoresistive sensor elements of such xMR sensors typically include aplurality of layers, of which at least one layer is a reference layerwith a reference magnetization (i.e., a reference direction). Thereference magnetization provides a sensing direction corresponding to asensing axis of the xMR sensor, thereby making the sensor element to amagnetic field component aligned in the sensing direction. A magneticfield component may be, for example, an x-magnetic field component (Bx),a y-magnetic field component (By), or a z-magnetic field component (Bz),where the Bx and By field components are in-plane to the chip, and Bz isout-of-plane to the chip in the examples provided. Accordingly, if amagnetic field component points exactly in the same direction as thereference direction, a resistance of the xMR sensor element is at amaximum, and, if a magnetic field component points exactly in theopposite direction as the reference direction, the resistance of the xMRsensor element is at a minimum.

In some applications, an xMR sensor includes a plurality ofmagnetoresistive sensor elements, which have the same or differentreference magnetizations. Examples of such applications, in whichvarious reference magnetizations are used, are angle sensors, compasssensors, or specific types of speed sensors (e.g., speed sensors in abridge arrangement referred to as monocells).

By way of example, such magnetoresistive sensor elements are used inspeed, angle, or rotational speed measuring apparatuses, in whichmagnets may be moved relative to an magnetoresistive sensor elements andhence the magnetic field at the location of the magnetoresistive sensorelement changes in the case of movement, which, in turn, leads to ameasurable change in resistance. For the purposes of an angle sensor, amagnet or a magnet arrangement may be applied to a rotatable shaft andan xMR sensor may be arranged stationary in relation thereto.

A Hall effect sensor is a transducer that varies its output voltage(Hall voltage) in response to a magnetic field. It is based on the Halleffect which makes use of the Lorentz force. The Lorentz force deflectsmoving charges in the presence of a magnetic field which isperpendicular to the current flow through the sensor or Hall plate.Thereby, a Hall plate can be a thin piece of semiconductor or metal. Thedeflection causes a charge separation which causes a Hall electricalfield. This electrical field acts on the charge in the oppositedirection with regard to the Lorentz Force. Both forces balance eachother and create a potential difference perpendicular to the directionof current flow. The potential difference can be measured as a Hallvoltage and varies in a linear relationship with the magnetic field forsmall values. Hall effect sensors can be used for proximity switching,positioning, speed detection, and current sensing applications.

A vertical Hall sensor is a magnetic field sensor constructed with theHall element perpendicular to the plane of the sensor chip (e.g.,extending from a main surface of the chip into the chip body). It sensesmagnetic fields perpendicular to its defined sensitive edge (top, right,or left, relative to the main surface of the chip). This generally meansthat a vertical Hall sensor is sensitive to a magnetic field componentthat extends parallel to their surface and parallel, or in-plane, to themain surface of the chip in which the vertical Hall sensor isintegrated. In particular, a vertical Hall sensor may extend from themain surface vertically into the chip (e.g., into a semiconductorsubstrate). The plane of sensitivity may be referred to herein as a“sensitivity-axis” or “sensing axis” and each sensing axis has areference direction. For vertical Hall sensor elements, voltage valuesoutput by the sensor elements change according to the magnetic fieldstrength in the direction of its sensing axis. For the purposes of thisdisclosure, a main surface of the sensor chip is defined in the XY planeand a vertical Hall sensor is sensitive to a field in the XY plane(e.g., in the X direction, Y direction, or a direction therebetween).

On the other hand, a lateral (planar) Hall sensor is constructed withthe Hall element in the same plane as the main surface of the sensorchip. It senses magnetic fields perpendicular to its planar surface.This means they are sensitive to magnetic fields vertical, orout-of-plane, to the main surface of the chip. The plane of sensitivitymay be referred to herein as a “sensitivity-axis” or “sensing axis” andeach sensing axis has a reference direction. Similar to vertical Hallsensor elements, voltage values output by lateral Hall sensor elementschange according to the magnetic field strength in the direction of itssensing axis. For the purposes of this disclosure, a main surface of thesensor chip is defined in the XY plane and a lateral Hall sensor issensitive to a field aligned in a Z direction that is perpendicular tothe XY plane.

FIGS. 1A and 1B illustrate a magnetic field sensing principle of amagnetic sensor system 100 according to one or more embodiments. Themagnetic sensor system 100 includes a toothed wheel 1 that hasalternating teeth 2 and notches 3. The teeth 2 and notches 3 arearranged in an alternating tooth-notch pattern and define acircumferential perimeter of the toothed wheel 1. The toothed wheel 1also includes an interior cavity 4 that is arranged within and isdefined by the circumferential perimeter. In some instances, the toothedwheel 1 may be a stamped wheel manufactured by a mechanical press thatis used to form the interior cavity 4 and the “L shape” of the teeth.

The toothed wheel 1 is configured to rotate about a rotation axis 5 thatextends in an axial direction. In this example, the axial direction isdefined by a y-axis and the teeth 2 and notches 3 are located away fromthe rotation axis 5 in different radial directions that are orthogonalto the rotation axis. The x-axis and z-axis are examples of two radialdirections that are orthogonal to the rotation axis. The toothed wheel 1further includes a support structure 6, such as a wheel disc, thatextends radially between the rotation axis 5 and the plurality of teeth2, wherein each of the plurality of teeth 2 extends from the supportstructure 5 in the axial direction to define the circumferentialperimeter. In other words, the teeth 2 protrude from the supportstructure 5 in the y-direction, parallel to the rotation axis in theillustrated example. The interior cavity 4 is formed in the area insidethe teeth protrusions and can be said to extend between two teeth thatare arranged on opposite sides of the wheel diameter.

The magnetic sensor system 100 further includes a front-bias magnet 110arranged within the interior cavity 4 of the toothed wheel 1. Thefront-bias magnet 110 is rotationally fixed in that it does not rotatewith the toothed wheel 1 but remains in a fixed position relative to thetoothed wheel 1. The front-bias magnet 110 is magnetized with amagnetization direction that extends along a radial axis 7 of thetoothed wheel 1, the radial axis 7 being orthogonal to the rotation axis5. In this case, z-axis represents the radial axis 7 and themagnetization direction extends in the +z-direction or −z-direction ofthe z-axis. IN other words, the magnetization direction can point in thenegative direction or in the positive direction of the radial axis 7.

The front-bias magnet 110 can be a diametrically magnetized magnet or anaxially magnetized magnet, as long as its magnetization directionextends along a defined radial axis 7 of the toothed wheel 1. Inaddition, the front-bias magnet 110 need not be a zero-gauss magnet thatrequires a bore that extends through its symmetry axis, such as a ringmagnet or a bored cylinder magnet. Instead, the front-bias magnet 110can be a simple block magnet, disc magnet, or cylinder magnet that is ofan entirely solid construction (i.e., with no bore present). Forexample, the front-bias magnet 110 can be a block magnet, an axiallymagnetized cylinder magnet, or a diametrically magnetized disc magnet.The radial axis 7 (e.g., z-axis) that coincides with the magnetizationdirection of the front-bias magnet 110 extends through an axis ofsymmetry of the front-bias magnet 110.

The magnetic sensor system 100 further includes a magnetic sensor 120arranged exterior to the toothed wheel 1. Like the front-bias magnet110, the magnetic sensor 120 is rotationally fixed in that it does notrotate with the toothed wheel 1 but remains in a fixed position relativeto the toothed wheel 1. This means that the magnetic sensor 120 alsoremains in a fixed position relative to the front-bias magnet 110. Themagnetic sensor 120 includes at least one sensor element arranged on theradial axis 7 (e.g., z-axis), or an extension thereof, that coincideswith the magnetization direction of the front-bias magnet 110. If morethan one sensor element is present, each sensor element is arranged onthe radial axis 7 (e.g., z-axis), or an extension thereof, thatcoincides with the magnetization direction of the front-bias magnet 110.

Furthermore, each sensor element is sensitive to a magnetic field of thefront-bias magnet 110 that is aligned with the radial axis 7 (e.g.,z-axis). That is, each sensor element has its sensitivity-axis alignedwith this radial axis 7 for sensing a magnetic field component of themagnetic field that coincides with the magnetization direction of thefront-bias magnet 110. In this example, each sensor element has asensitivity-axis aligned with the positive z-direction for measuring themagnetic field component Bz or has its sensitivity-axis aligned with thenegative z-direction for measuring the magnetic field component −Bz. Inthe case of multiple sensor elements, the sensitivity-axes of the sensorelements all point in the same direction.

In the case that xMR sensor elements, the resistance values of the xMRsensor elements change depending on the magnetic field strength in thedirection of the sensitivity-axis, and the resistance values of the xMRsensor elements may be detected by a sensor circuit of the magneticsensor 120 or may be output from the senor element as a voltage valuethat is representative of the resistance value (i.e., the voltage valuechanges as the resistance value changes). In the former case, theresistance value is output as a sensor signal, and, in the latter case,the voltage value is output as a sensor signal, however, the sensorsignal is not limited thereto.

Alternatively, the sensor elements may be vertical or lateral Hallsensor elements that have a sensitivity-axis that is aligned with themagnetic field component that coincides with the magnetization directionof the front-bias magnet 110 (i.e., that coincides with the radial axis7). In Hall sensor elements, voltage values output by the sensorelements change according to the magnetic field strength in thedirection of the sensitivity-axis.

The magnetic sensor system 100 is configured such that tooth of thetoothed wheel 1 shields the magnetic sensor 120 from the magnetic fieldproduced by the front-bias magnet 110 such that substantially nomagnetic field is detected at the sensor elements of the magnetic sensor120 and each notch the toothed wheel 1 exposes the magnetic sensor 120to the magnetic field produced by the front-bias magnet 110 such that acertain magnetic field strength is detectable at the sensor elements ofthe magnetic sensor 120. The certain magnetic field strength depends, inpart, on the air-gap or distance between the front-bias magnet 110 andthe magnetic sensor 120. The smaller the air-gap or distance, thegreater the magnetic field strength. Naturally, the magnetic fieldstrength also depends on how strongly the magnet is magnetized, thematerial of the magnet, etc.

The certain magnetic field strength may be a detected as a positivevalue or a negative value depending on whether the magnetizationdirection and the sensitivity-axes point in the negative direction(i.e., the −z-direction) or the positive direction of the radial axis 7,and more particularly, whether the sensitivity-axes are pointingparallel or anti-parallel to the magnetization direction. In eithercase, the absolute value of the magnetic field strength present at thesensor elements when a center of a notch passes between the front-biasmagnet 110 and the magnetic sensor 120 is much greater than the absolutevalue of the magnetic field strength present at the sensor elements whena center of a tooth passes between the front-bias magnet 110 and themagnetic sensor 120. In particular, a zero or a substantially zero(e.g., ˜0 mT) magnetic offset is present at the sensor elements of themagnetic sensor 120 each time a center of a tooth passes between thefront-bias magnet 110 and the magnetic sensor 120 as a result of themagnetic shielding provided by the teeth 2. Thus, substantially nomagnetic field is detected at the sensor elements of the magnetic sensor120 when a center of a tooth passes between the front-bias magnet 110and the sensor elements.

Accordingly, as the toothed wheel 1 rotates about its rotation axis 5,the teeth 2 and the notches 3 alternate passed the space between thefront-bias magnet 110 and the magnetic sensor 120. This rotation of thetoothed wheel 1 causes the magnetic field to oscillate between a firstextremum value (e.g., certain positive or negative magnetic fieldstrength) and a second extremum value (e.g., 0 mT) at a location of asensor element. This, in turn, causes a sensor signal generated by asensor element to oscillate between two extrema values proportional tothe sensed magnetic field strength.

For example, a sensor element is configured to generate a sensor signalin response to sensing the oscillating magnetic field modulated by therotation of the toothed wheel 1, and the sensor signal has a signalpattern representative of the tooth-notch pattern of the toothed wheel1. In particular, the sensor signal may have a first signal valuerepresentative of the first extremum value of the magnetic field when acenter of any notch is interposed between the front-bias magnet 110 andthe sensor element, and the sensor signal has a second signal valuerepresentative of the second extremum value of the magnetic field when acenter of any tooth is interposed between the front-bias magnet 110 andthe sensor element. Due to the shielding effect of the teeth 2, thesecond extremum value of the magnetic field is substantially zero and anabsolute value of the first extremum value is greater than an absolutevalue of the second extremum value.

FIG. 2 illustrates a cross-sectional view of a magnetic sensor system200 according to one or more embodiments. The magnetic sensor system 200applies the magnetic field sensing principle described in conjunctionwith FIGS. 1A and 1B. In this example, the front-bias magnet 110 isarranged inside the interior cavity 4 of the toothed wheel 1 and themagnetic sensor 120 is arranged outside of the toothed wheel 1 such thatthe teeth 2 of the toothed wheel 1 pass between the front-bias magnet110 and the magnetic sensor 120 as the toothed wheel 1 rotates about itsrotation axis 5. However, it will be appreciated that this arrangementcould be reversed while still achieving the same result. In other words,the magnetic sensor 120 could be arranged inside the interior cavity 4of the toothed wheel 1 and the front-bias magnet 110 could be arrangedoutside of the toothed wheel 1. In this setup, the teeth 2 still shieldthe magnetic sensor 120 from the magnetic field.

The magnetic sensor 120 includes a first sensor element 121 that has itssensitivity-axis aligned with the radial axis 7 and pointing in thepositive z-direction. The radial axis 7 extends through both the firstsensor element 121 and the axis of symmetry of the front-bias magnet110, in alignment with (i.e., coincides with) the magnetizationdirection of the front-bias magnet 110. The first sensor element 121 isarranged at a first distance d1 from the tooth 2 along the radial axis 7and thus has a specific distance from the front-bias magnet 110. Themagnetic sensor 120 may also include an optional second sensor element122 that has its sensitivity-axis aligned with the radial axis 7 andpointing in the positive z-direction. The radial axis 7 extends throughboth the second sensor element 122 and the axis of symmetry of thefront-bias magnet 110, in alignment with (i.e., coincides with) themagnetization direction of the front-bias magnet 110. The second sensorelement 122 is arranged at a second distance d2 from the tooth 2 alongthe radial axis 7 and thus has a specific distance from the front-biasmagnet 110. The two sensor elements 121 and 122 are also spaced apartfrom each other along the radial axis 7 by a distance referred to as asensor pitch.

While the magnetic field will be substantially zero when a center of atooth passes between the front-bias magnet 110 and the magnetic sensor120, the magnetic field at the two sensor elements 121 and 122 will bedifferent when a center of a notch passes between the front-bias magnet110 and the magnetic sensor 120 due to the difference in distancesbetween d1 and d2 along the radial axis. For example, the magnetic fieldstrength at sensor element 121 will be greater than the magnetic fieldstrength at sensor element 121 due to the different distances.

The inclusion of two sensor elements 121 and 122 provides a differentialsensing principle that allows external magnetic stray-fields to becanceled out by differential calculus. For example, externalstray-fields in the sensor plane (e.g., aligned along the z-axis) willcancel out due to the differential calculus applied to the two sensorsignals and out-of-plane magnetic field components do not affect thesensor output because the sensor elements 121 and 122 are not sensitivethereto. The sensor circuit may be configured to combine the two sensorsignals to generate a differential signal that is independent ofexternal stray-fields. For example, the sensor signal generated by oneof the sensor elements may be subtracted from the other sensor signal toobtain the differential signal.

It will be appreciated that the differential measurement principle couldbe also realized by sensor elements arranged in a Wheatstone bridgeconfiguration, where the output of the Wheatstone bridge is adifferential signal. For example, four xMR sensor elements may beconnected in a Wheatstone bridge, with one sensor element located in adifferent segment or branch of the Wheatstone bridge. Respective pairsof xMR sensor elements of the Wheatstone bridge are located atessentially the same distance (two xMR sensor elements at distance d1close to the magnet and the other two xMR sensor elements at thedistance d2). The differential bridge output voltage will cancelhomogeneous stray-fields. Thus, this differential bridge output voltagemay be used as the differential signal.

In addition, the sensing capabilities of the magnetic sensor 120 isindependent of the air-gap between the magnetic sensor 120 and the toothwheel 1 or the front-bias magnet 110. That is, the magnetic sensor 120is tolerant to manufacturing and assembly errors during which the exactair-gap between the magnetic sensor 120 and the tooth wheel 1 maydiffer. Small differences in this air-gap along the radial axis 7 thatmay occur during assembly does not negatively impact the ability of themagnetic sensor 120 to detect wheel speed or its ability to discriminatethe presence of a notch or a tooth between the magnetic sensor 120 andthe tooth wheel 1 or the front-bias magnet 110. The sensor elements 121and 122 are twist-insensitive such that the sensor will work independentfrom a mounting position regardless of its rotational orientation aroundthe z-axis.

In this example, the two sensor elements 121 and 122 may be xMR sensorelements or vertical Hall sensor elements, both technologies allow thesensitivity-axes to be aligned with the magnetization direction in thissetup. The two sensor elements 121 and 122 may be integrated in a sensorchip 123 of the magnetic sensor 120 that is encapsulated by a sensorpackage 124 (e.g., molding). As will be discussed below, the sensor chip123 may include a sensor circuit that receives and processes the sensorsignals generated by the sensor elements 121 and 122. The magneticsensor 120 may also include a chip carrier or lead 125 that electricallyconnects the sensor circuit to an external device, such as an externalcontroller, which may be an electronic control unit (ECU).

The rotation of the toothed wheel causes the magnetic field to oscillatebetween a first extremum value and a second extremum value at a locationof the first sensor element 121 and causes the magnetic field tooscillate between a third extremum value and a fourth extremum value ata location of the second sensor element 122. The second and the fourthextremum values of the magnetic field are substantially zero due theshielding effect of the teeth 2 that produces a zero magnetic offset atthe sensor elements. The first and the third extremum values of themagnetic field are different due to the difference between distances d1and d2.

As a result, the first sensor element 121 is configured to generate afirst sensor signal in response to sensing the oscillating magneticfield modulated by the rotation of the toothed wheel 1 and the secondsensor element 121 is configured to generate a second sensor signal inresponse to sensing the oscillating magnetic field modulated by therotation of the toothed wheel 1.

The first sensor signal has a first extremum signal value representativeof the first extremum value of the magnetic field when a center of anynotch is interposed between the front-bias magnet 110 and the firstsensor element 121. The first extremum signal value may be a positive(maximum) value or a negative (minimum) value depending on whether thesensitivity-axis of sensor element 121 is parallel or anti-parallel tothe magnetization direction. The first sensor signal has a secondextremum signal value representative of the second extremum value of themagnetic field when a center of any tooth is interposed between thefront-bias magnet and the first sensor element. The second extremumsignal value may be zero or substantially zero, corresponding to thesubstantially zero magnetic offset.

The second sensor signal has a third extremum signal valuerepresentative of the third extremum value of the magnetic field when acenter of any notch is interposed between the front-bias magnet and thesecond sensor element. The third extremum signal value may be a positive(maximum) value or a negative (minimum) value depending on whether thesensitivity-axis of sensor element 122 is parallel or anti-parallel tothe magnetization direction. The second sensor signal has a fourthextremum signal value representative of the fourth extremum value of themagnetic field when a center of any tooth is interposed between thefront-bias magnet 110 and the second sensor element 122. The fourthextremum signal value may be zero or substantially zero, correspondingto the substantially zero magnetic offset.

The sensor circuit of the magnetic sensor 120 may be configured toreceive the first sensor signal and the second sensor signal, generate adifferential signal based on a combination of the first sensor signaland the second sensor signal, and generate a pulsed output signal basedon the differential sensor signal crossing at least one threshold. Forexample, the sensor circuit may compare the differential signal to apredetermined switching threshold (e.g., a middle value between twoexpected extrema values of the differential signal) and generate asignal pulse each time the differential signal crosses the switchingthreshold. Alternatively, a signal pulse may be generated only on arising or on a falling transition of the differential signal. In anycase, the frequency of the pulses corresponds to a speed of rotation ofthe wheel, which further corresponds to a speed of rotation of a driveshaft (e.g., camshaft) that drives the rotation of the wheel.

In addition, the sensor circuit may be configured to determine whether anotch or a tooth is located between the front-bias magnet 110 and themagnetic sensor 120 based on at least one of the first sensor signal,the second sensor signal, or the differential signal. For example, thesensor circuit may compare one of the first sensor signal, the secondsensor signal, or the differential signal to a predetermined threshold.If the signal is on the side of the threshold closer to zero, the sensorcircuit may determine that a tooth is located between the front-biasmagnet 110 and the magnetic sensor 120. If the signal is substantiallyzero, the sensor circuit may determine that a center of a tooth islocated between the front-bias magnet 110 and the magnetic sensor 120.In contrast, if the signal is on the side of the threshold closer to amaximum positive value or minimum negative value, the sensor circuit maydetermine that a notch is located between the front-bias magnet 110 andthe magnetic sensor 120. If the signal is substantially at the maximumpositive value or the minimum negative value, the sensor circuit maydetermine that a center of a notch is located between the front-biasmagnet 110 and the magnetic sensor 120.

FIG. 3 illustrates a cross-sectional view of a magnetic sensor system300 according to one or more embodiments. The magnetic sensor system 300applies the magnetic field sensing principle described in conjunctionwith FIGS. 1A and 1B and includes features that are similar to magneticsensor system 200. It will be appreciated that this arrangement could bereversed such that the magnetic sensor 120 is arranged inside theinterior cavity 4 of the toothed wheel 1 and the front-bias magnet 110is arranged outside of the toothed wheel 1.

The magnetic sensor 120 is a monocell configuration that includes onlyone sensor element, the first sensor element 121, that has itssensitivity-axis aligned with the radial axis 7. In this example, thesensor element 121 may be a lateral Hall sensor element or a z-sensitivexMR sensor element, both technologies allow the sensitivity-axes to bealigned with the magnetization direction in this setup. The sensorelement 121 is twist-insensitive such that the sensor will workindependent from a mounting position regardless of its rotationalorientation around its z-axis.

The sensor circuit of the magnetic sensor 120 may be configured toreceive the first sensor signal and generate a pulsed output signalbased on the first sensor signal crossing at least one threshold. Forexample, the sensor circuit may compare the first sensor signal to apredetermined switching threshold (e.g., an intermediate value betweentwo expected extrema values of the differential signal) and generate asignal pulse each time the first sensor signal crosses the switchingthreshold. Alternatively, a signal pulse may be generated only on arising or on a falling transition of the first sensor signal. In anycase, the frequency of the pulses corresponds to a speed of rotation ofthe wheel, which further corresponds to a speed of rotation of a driveshaft (e.g., camshaft) that drives the rotation of the wheel.

In addition, the sensor circuit may be configured to determine whether anotch or a tooth is located between the front-bias magnet 110 and themagnetic sensor 120 based on the first sensor signal. For example, thesensor circuit may compare the first sensor signal to a predeterminedthreshold. If the first sensor signal is on the side of the thresholdcloser to zero, the sensor circuit may determine that a tooth is locatedbetween the front-bias magnet 110 and the magnetic sensor 120. If thefirst sensor signal is substantially zero, the sensor circuit maydetermine that a center of a tooth is located between the front-biasmagnet 110 and the magnetic sensor 120. In contrast, if the first sensorsignal is on the side of the threshold closer to a maximum positivevalue or minimum negative value, the sensor circuit may determine that anotch is located between the front-bias magnet 110 and the magneticsensor 120. If the first sensor signal is substantially at the maximumpositive value or the minimum negative value, the sensor circuit maydetermine that a center of a notch is located between the front-biasmagnet 110 and the magnetic sensor 120.

FIG. 4 illustrates a cross-sectional view of a magnetic sensor system400 according to one or more embodiments. The magnetic sensor system 400applies the magnetic field sensing principle described in conjunctionwith FIGS. 1A and 1B and includes features that are similar to magneticsensor system 200. It will be appreciated that this arrangement could bereversed such that the magnetic sensor 120 is arranged inside theinterior cavity 4 of the toothed wheel 1 and the front-bias magnet 110is arranged outside of the toothed wheel 1.

The magnetic sensor 120 has a differential sensing configuration thatincludes both the first sensor element 121 and the second sensor element122. As in FIG. 2 , the first sensor element 121 and the second sensorelement 122 have their sensitivity-axes aligned with the radial axis 7.In this example, the sensor elements 121 and 122 may be a lateral Hallsensor element or a z-sensitive xMR sensor element, both technologiesallow the sensitivity-axes to be aligned with the magnetizationdirection in this setup. In addition, the magnetic sensor 120 includestwo sensor chips 123 a and 123 b arranged on opposite sides of the chipcarrier or lead 125 so that the sensor elements 121 and 122 can bearranged at different distances d1 and d2 from the toothed wheel 1 (andfrom the front-bias magnet 110).

The two chips 123 a and 123 b may include a common sensor circuit (e.g.,a common processor) that receives and processes the sensor signalsgenerated by the sensor elements 121 and 122, for example, to generate adifferential signal. That is, one of the chips may process both sensorsignals to, for example, generate the differential signal, calculate thewheel speed, the detect the present of a tooth or a notch forTrue-power-on (TPO). The two chips 123 a and 123 b may electricallyconnected via the chip carrier or lead 125. Alternatively, the twosensor signals may be output to an external controller for processing.

As a result of this setup, the magnetic sensor 120 is bothtwist-insensitive such that the sensor will work independent from amounting position regardless of its rotational orientation around itsz-axis and is robust against external magnetic stray-fields due to thedifferential sensing principle.

The sensor circuit of the magnetic sensor 120 may be configured toreceive the first sensor signal and the second sensor signal, generate adifferential signal based on a combination of the first sensor signaland the second sensor signal, and generate a pulsed output signal basedon the differential sensor signal crossing at least one threshold. Inaddition, the sensor circuit may be configured to determine whether anotch or a tooth is located between the front-bias magnet 110 and themagnetic sensor 120 based on at least one of the first sensor signal,the second sensor signal, or the differential signal.

FIG. 5A is a schematic block diagram of a sensor circuit 500A for amonocell sensing configuration according to one or more embodiments.FIG. 5B is a schematic block diagram of a sensor circuit 500B for adifferential sensing configuration according to one or more embodiments.

Sensor circuit 500A includes sensor element 121 that generates a sensorsignal 51 as an analog signal (e.g., an analog voltage), an optionalamplifier 501 that amplifies sensor signal 51, and ADC 502 that convertsthe amplified signal into a digital sensor signal, and a signalprocessor 503 that processes the digital sensor signal. For example, thesignal processor 503 may compare the digital sensor signal to one ormore switching thresholds for generating a pulsed output signal Sout,the pulses of which are representative of the wheel speed of the toothwheel 1. The signal processor 503 may include a current modulator, alsoreferred to as a protocol generator, that receives the output of acomparator and generates the pulsed output signal Sout as an outputcurrent according to a programmed current switching protocol or ruleset.

Additionally, the signal processor 503 may compare the digital sensorsignal to one or more position thresholds or compare the value of thedigital sensor signal to values listed in a look-up table for generatinga position output signal Pout. In particular, the signal processor 503may use the one or more position thresholds for determining the positionof the toothed wheel 1, including whether a tooth or a notch ispresently between the front-bias magnet 110 and the magnetic sensor 120.In this way, the signal processor 503 determines whether a notch or atooth is located between the front-bias magnet and the magnetic sensorbased on the sensor signal. Thus, the position output signal Pout mayindicate whether a tooth or a notch is presently between the front-biasmagnet 110 and the magnetic sensor 120, which may be used for TPO.

Sensor circuit 500B includes the first sensor element 121 that generatesa sensor signal 51 as an analog signal (e.g., an analog voltage) and thesecond sensor element 122 that generates a sensor signal S2 as an analogsignal (e.g., an analog voltage). The sensor circuit 500B additionallyincludes an optional amplifier 504, a differential comparator 505, anADC 506, and the signal processor 503. The amplifier 504 amplifies thedifferential sensor signals 51 and S2 according to a set gain andprovides the amplified differential sensor signals to the differentialcomparator 505. The differential comparator 505 converts thedifferential sensor signals to an analog differential measurement signalhaving a value equal to the voltage difference between the amplifieddifferential sensor signals. The ADC 506 converts the analogdifferential measurement signal into the digital domain, specifically,into a digital differential measurement signal representative of thevoltage difference between sensor signals 51 and S2. The signalprocessor 503 processes the digital differential measurement signal in asimilar manner described above in reference to sensor circuit 500A togenerate a pulsed output signal Sout and a position output signal Pout.

FIGS. 6A and 6B illustrate sensor packages according to one or moreembodiments. In FIG. 6A, the front-bias magnet 110 is arranged insidethe interior cavity 4 of the toothed wheel 1 and the magnetic sensor 120is arranged external to the toothed wheel 1. In FIG. 6B, the magneticsensor 120 is arranged inside the interior cavity 4 of the toothed wheel1 and the front-bias magnet 110 is arranged external to the toothedwheel 1. The front-bias magnet 110 is magnetized with a magnetizationdirection that extends along a symmetry axis of the front-bias magnet110.

In both FIGS. 6A and 6B, the front-bias magnet 110 and the magneticsensor 120 are encapsulated by a molded package 600 (e.g., encapsulant).The molded package 600 has a one-piece integral construction that holdsthe symmetry axis of the magnet 110 in alignment with thesensitivity-axis of each sensor element of the magnetic sensor 120.Here, the magnetic sensor 120 includes at least one sensor elementarranged on an extension of the symmetry axis that coincides with themagnetization direction of the front-bias magnet 110, where each sensorelement is sensitive to a magnetic field of the front-bias magnet 110that is aligned with the symmetry axis.

The molded package 600 has a package notch 601 formed between thefront-bias magnet 110 and the magnetic sensor 120 along the extension ofthe symmetry axis of the front-bias magnet 110 (e.g., along an extensionof the radial axis 7). The package notch 601 is formed to enable theteeth 2 of the toothed wheel 1 to pass through the package notch 601during a rotation of the toothed wheel 1. Thus, the package notch 610allows the toothed wheel 1 to freely rotate while maintaining thefront-bias magnet 110 and the magnetic sensor 120 in their fixedpositions. In this way, the magnetic sensor 120 is shielded from orexposed to the magnetic field of the magnetic 110 as the toothed wheel 1rotates about its rotation axis 5.

In the above-described embodiments, the low magnetic field offset thatcan be seen by the sensor in the region of the tooth 2 of the toothwheel 1 can also be useful for the lifetime stability and true power onfeature. TPO means the sensor circuit is able to detect directly atstartup the correct position of the wheel 1 (e.g., it detects whetherthere is a tooth or notch in front of it). This is realized by athreshold value. If the sensed field exceeds the threshold, then thereis a notch. If the sensed field is smaller than the threshold, thenthere is a tooth. In case of magnet degradation over its lifetime (i.e.,magnet loses its strength), the magnetic offset will still be at orclose to zero. Thus, there is little to no impact on the performance ofthe sensor or its capability to detect a tooth or notch at startupdespite a degradation of the magnet. Moreover, expensive zero-gaussmagnets are not needed, providing a cost-effective solution. Lessexpensive magnetics can be used instead. Moreover, a higher air-gapcapability is achieved.

While the above embodiments are described in the context of detecting awheel or camshaft speed, the sensor may be used to detect the rotationspeed of any rotating member or object that creates sinusoidalvariations in a magnetic field as it rotates and that may be sensed by asensor, including a crankshaft and transmission speed sensing. Forexample, a combination of a ferrous wheel and a back-bias magnet may beused to generate a time varying magnetic field.

Further, while various embodiments have been described, it will beapparent to those of ordinary skill in the art that many moreembodiments and implementations are possible within the scope of theinvention. Accordingly, the invention is not to be restricted except inlight of the attached claims and their equivalents. With regard to thevarious functions performed by the components or structures describedabove (assemblies, devices, circuits, systems, etc.), the terms(including a reference to a “means”) used to describe such componentsare intended to correspond, unless otherwise indicated, to any componentor structure that performs the specified function of the describedcomponent (i.e., that is functionally equivalent), even if notstructurally equivalent to the disclosed structure that performs thefunction in the exemplary implementations of the invention illustratedherein.

Furthermore, the following claims are hereby incorporated into thedetailed description, where each claim may stand on its own as aseparate example embodiment. While each claim may stand on its own as aseparate example embodiment, it is to be noted that—although a dependentclaim may refer in the claims to a specific combination with one or moreother claims—other example embodiments may also include a combination ofthe dependent claim with the subject matter of each other dependent orindependent claim. Such combinations are proposed herein unless it isstated that a specific combination is not intended. Furthermore, it isintended to include also features of a claim to any other independentclaim even if this claim is not directly made dependent to theindependent claim.

It is further to be noted that methods disclosed in the specification orin the claims may be implemented by a device having means for performingeach of the respective acts of these methods.

Further, it is to be understood that the disclosure of multiple acts orfunctions disclosed in the specification or claims may not be construedas to be within the specific order. Therefore, the disclosure ofmultiple acts or functions will not limit these to a particular orderunless such acts or functions are not interchangeable for technicalreasons. Furthermore, in some embodiments a single act may include ormay be broken into multiple sub acts. Such sub acts may be included andpart of the disclosure of this single act unless explicitly excluded.

1. A magnetic sensor system, comprising: a toothed wheel configured torotate about a rotation axis that extends in an axial direction, whereinthe toothed wheel comprises a plurality of teeth and a plurality ofnotches arranged in an alternating tooth-notch pattern and which definea circumferential perimeter, and wherein the toothed wheel furthercomprises an interior cavity arranged within the circumferentialperimeter; a front-bias magnet arranged within the interior cavity ofthe toothed wheel, wherein the front-bias magnet is rotationally fixedand is magnetized with a magnetization direction that extends along aradial axis of the toothed wheel, the radial axis being orthogonal tothe rotation axis; and a magnetic sensor arranged exterior to thetoothed wheel, wherein the magnetic sensor comprises a first sensorelement arranged on the radial axis that coincides with themagnetization direction of the front-bias magnet and the first sensorelement is sensitive to a magnetic field of the front-bias magnet thatis aligned with the radial axis, and wherein a rotation of the toothedwheel causes the magnetic field to oscillate between a first extremumvalue and a second extremum value at a location of the first sensorelement.
 2. The magnetic sensor system of claim 1, wherein the toothedwheel further comprises a support structure that extends radiallybetween the rotation axis and the plurality of teeth, and wherein eachof the plurality of teeth extends from the support structure in theaxial direction to define the circumferential perimeter.
 3. The magneticsensor system of claim 2, wherein the toothed wheel is a stamped wheel.4. The magnetic sensor system of claim 1, wherein the front-bias magnetis a diametrically magnetized magnet or an axially magnetized magnet. 5.The magnetic sensor system of claim 1, wherein the radial axis thatcoincides with the magnetization direction of the front-bias magnetextends through an axis of symmetry of the front-bias magnet.
 6. Themagnetic sensor system of claim 1, wherein the front-bias magnet has anentirely solid construction.
 7. The magnetic sensor system of claim 6,wherein the front-bias magnet is a block magnet, an axially magnetizedcylinder magnet, or a diametrically magnetized disc magnet.
 8. Themagnetic sensor system of claim 1, wherein each tooth of the pluralityof teeth is configured to shield the magnetic sensor from the magneticfield and each notch of the plurality of notches is configured to exposethe magnetic sensor to the magnetic field.
 9. The magnetic sensor systemof claim 8, wherein the first sensor element is configured to generate afirst sensor signal in response to sensing the magnetic field modulatedby the rotation of the toothed wheel, and wherein the first sensorsignal has a signal pattern representative of the alternatingtooth-notch pattern.
 10. The magnetic sensor system of claim 9, wherein:the first sensor signal has a first signal value representative of thefirst extremum value of the magnetic field when a center of any notch isinterposed between the front-bias magnet and the first sensor element,and the first sensor signal has a second signal value representative ofthe second extremum value of the magnetic field when a center of anytooth is interposed between the front-bias magnet and the first sensorelement.
 11. The magnetic sensor system of claim 10, wherein the secondextremum value of the magnetic field is substantially zero and anabsolute value of the first extremum value is greater than an absolutevalue of the second extremum value.
 12. The magnetic sensor system ofclaim 1, wherein the second extremum value of the magnetic field issubstantially zero and an absolute value of the first extremum value isgreater than an absolute value of the second extremum value.
 13. Themagnetic sensor system of claim 9, wherein the magnetic sensor comprisesa sensor circuit configured to receive the first sensor signal andgenerate a pulsed output signal based on the first sensor signalcrossing at least one threshold.
 14. The magnetic sensor system of claim9, wherein the magnetic sensor comprises a sensor circuit configured toreceive the first sensor signal and determine whether a notch or a toothis located between the front-bias magnet and the magnetic sensor basedon the first sensor signal.
 15. The magnetic sensor system of claim 1,wherein the magnetic sensor comprises a second sensor element arrangedon the radial axis that coincides with the magnetization direction ofthe front-bias magnet and the second sensor element is sensitive to themagnetic field of the front-bias magnet that is aligned with the radialaxis, and wherein a rotation of the toothed wheel causes the magneticfield to oscillate between a third extremum value and a fourth extremumvalue at a location of the second sensor element.
 16. The magneticsensor system of claim 15, wherein the first sensor element is arrangedat a first distance from the front-bias magnet along the radial axis andthe second sensor element is arranged at a second distance from thefront-bias magnet along the radial axis that is different from the firstdistance.
 17. The magnetic sensor system of claim 15, wherein each toothof the plurality of teeth is configured to shield the magnetic sensorfrom the magnetic field and each notch of the plurality of notches isconfigured to expose the magnetic sensor to the magnetic field.
 18. Themagnetic sensor system of claim 17, wherein the first sensor element isconfigured to generate a first sensor signal in response to sensing themagnetic field modulated by the rotation of the toothed wheel and thesecond sensor element is configured to generate a second sensor signalin response to sensing the magnetic field modulated by the rotation ofthe toothed wheel, wherein the first sensor signal has a first extremumsignal value representative of the first extremum value of the magneticfield when a center of any notch is interposed between the front-biasmagnet and the first sensor element, wherein the first sensor signal hasa second extremum signal value representative of the second extremumvalue of the magnetic field when a center of any tooth is interposedbetween the front-bias magnet and the first sensor element, wherein thesecond sensor signal has a third extremum signal value representative ofthe third extremum value of the magnetic field when a center of anynotch is interposed between the front-bias magnet and the second sensorelement, and wherein the second sensor signal has a fourth extremumsignal value representative of the fourth extremum value of the magneticfield when a center of any tooth is interposed between the front-biasmagnet and the second sensor element.
 19. The magnetic sensor system ofclaim 18, wherein the second and the fourth extremum values of themagnetic field are substantially zero.
 20. The magnetic sensor system ofclaim 15, wherein the second and the fourth extremum values of themagnetic field are substantially zero.
 21. The magnetic sensor system ofclaim 18, wherein the magnetic sensor comprises a sensor circuitconfigured to: receive the first sensor signal and the second sensorsignal, generate a differential signal based on a combination of thefirst sensor signal and the second sensor signal, and generate a pulsedoutput signal based on the differential signal crossing at least onethreshold.
 22. The magnetic sensor system of claim 21, wherein themagnetic sensor comprises a sensor circuit configured to determinewhether a notch or a tooth is located between the front-bias magnet andthe magnetic sensor based on at least one of the first sensor signal,the second sensor signal, or the differential signal.
 23. The magneticsensor system of claim 15, wherein the first sensor element has asensitivity axis aligned with the radial axis that coincides with themagnetization direction of the front-bias magnet.
 24. The magneticsensor system of claim 15, wherein the first sensor element and thesecond sensor element each have a sensitivity axis aligned with theradial axis that coincides with the magnetization direction of thefront-bias magnet.
 25. The magnetic sensor system of claim 15, furthercomprising: a molded package that encapsulates the front-bias magnet andthe magnetic sensor, wherein the molded package comprises a packagenotch formed between the front-bias magnet and the magnetic sensor alongthe radial axis, and wherein the plurality of teeth are configured topass through the package notch during a rotation of the toothed wheel.26. A magnetic sensor system, comprising: a toothed wheel configured torotate about a rotation axis that extends in an axial direction, whereinthe toothed wheel comprises a plurality of teeth and a plurality ofnotches arranged in an alternating tooth-notch pattern and which definea circumferential perimeter, and wherein the toothed wheel furthercomprises an interior cavity arranged within the circumferentialperimeter; a front-bias magnet arranged exterior to the toothed wheel,wherein the front-bias magnet is rotationally fixed and is magnetizedwith a magnetization direction that extends along a radial axis of thetoothed wheel, the radial axis being orthogonal to the rotation axis;and a magnetic sensor arranged within the interior cavity of the toothedwheel, wherein the magnetic sensor comprises a first sensor elementarranged on the radial axis that coincides with the magnetizationdirection of the front-bias magnet and the first sensor element issensitive to a magnetic field of the front-bias magnet that is alignedwith the radial axis, and wherein a rotation of the toothed wheel causesthe magnetic field to oscillate between a first extremum value and asecond extremum value at a location of the first sensor element.
 27. Themagnetic sensor system of claim 26, wherein each tooth of the pluralityof teeth is configured to shield the magnetic sensor from the magneticfield and each notch of the plurality of notches is configured to exposethe magnetic sensor to the magnetic field.
 28. The magnetic sensorsystem of claim 27, wherein: the first sensor element is configured togenerate a first sensor signal in response to sensing the magnetic fieldmodulated by the rotation of the toothed wheel, wherein the first sensorsignal has a signal pattern representative of the alternatingtooth-notch pattern, the first sensor signal has a first signal valuerepresentative of the first extremum value of the magnetic field when acenter of any notch is interposed between the front-bias magnet and thefirst sensor element, and the first sensor signal has a second signalvalue representative of the second extremum value of the magnetic fieldwhen a center of any tooth is interposed between the front-bias magnetand the first sensor element.
 29. The magnetic sensor system of claim28, wherein the second extremum value of the magnetic field issubstantially zero and an absolute value of the first extremum value isgreater than an absolute value of the second extremum value.
 30. Amagnetic sensor module, comprising: a front-bias magnet magnetized witha magnetization direction that extends along a symmetry axis of thefront-bias magnet; a magnetic sensor comprising a first sensor elementarranged on an extension of the symmetry axis that coincides with themagnetization direction of the front-bias magnet, wherein the firstsensor element is sensitive to a magnetic field of the front-bias magnetthat is aligned with the symmetry axis; and a molded package thatencapsulates the front-bias magnet and the magnetic sensor, wherein themolded package comprises a package notch formed between the front-biasmagnet and the magnetic sensor along the extension of the symmetry axis.31. The magnetic sensor module of claim 30, wherein the molded packagehas a one-piece integral construction.